Are you playing softcore, or hardcore? If you’re playing softcore, there’s nothing stopping you from turning the difficulty up and just seeing how you go at torment 2/3/4 etc. If the monsters completely wipe the floor with you, lower the difficulty, and continue grinding it out at a level you’re comfortable with until you find stronger gear, and can increase the difficulty. The general advice is to play at a difficulty where you can complete a rift in between 2 and 4 minutes 
Meteorblade has put together an excellent guide here which may be of help to you too.